Saunas and Your Health

By Harvard Health Publications

Sweating is an impulse that extends far back in human history. About 3,000 years ago, the Mayans of Central America used sweat houses for religious ceremonies and good health. Nearly every culture has its own way of using heat for relaxation, therapy, and ritual; ancient Roman baths, modern Turkish steam baths, and trendy American hot tubs are but a few examples. One of the oldest and hottest of these techniques is the sauna. Saunas have been used for thousands of years in Finland, where nearly a third of all adults take them regularly. And saunas are increasingly popular in the United States, where over one million are in use. Popularity is one thing, safety another. Are saunas good for your health, or can they be harmful?

Inside the box

The modern sauna is a simple unpainted room with wooden walls and benches. Heat is provided by a rock-filled electric heater and it gets plenty hot. The recommended temperature rises from about 90°F at floor level to about 185°F at the top. Unlike Turkish baths, Finnish saunas are very dry, maintaining humidity levels of just 10% - 20%. Water drains through the floor to keep things dry. In a good sauna, an efficient ventilation system exchanges the air three to eight times an hour.

Experienced sauna bathers usually stay inside for periods of 5 - 20 minutes; after a cooling-off period, some return for a second session. And people in the know always remember to drink plenty of fluids after their saunas.

The dry heat has profound effects on the body. Sweating begins almost immediately. The average person will pour out a pint of sweat during his brief sauna, but it evaporates so quickly in the dry air that people may not realize how much they perspire. Skin temperature soars to about 104°F within minutes, but internal temperatures rise more slowly and usually stay below 100°F.

Changes in body temperature are easy to understand, but the cardiovascular responses to heat are even more important. The pulse rate jumps by 30% or more, allowing the heart to nearly double the amount of blood it pumps each minute. Most of the extra blood flow is directed to the skin; in fact, the circulation actually shunts blood away from the internal organs. The blood pressure is unpredictable, rising in some people but falling in others. All of these changes resolve quickly after people cool down.

Although a sauna may help you relax, your heart is working hard while you sit on your bench.

The heart of the matter

Saunas appear safe for patients with stable coronary artery disease, and a small study from Japan suggested that two weeks of daily saunas may even improve vascular function in patients with stable congestive heart failure. Still, heart patients should check with their doctors before using saunas. People who can perform moderate exercise such as walking for 30 minutes or climbing three or four flights of stairs without stopping will likely get an okay, but patients with poorly controlled blood pressure, abnormal heart rhythms, unstable angina, and advanced heart failure or heart valve disease will be advised to stay cool.

Other organs

Although saunas affect many parts of the body, most changes are brief and mild. For example, elevated scrotal temperatures reduce sperm production, but there is no evidence that regular saunas impair fertility. The dry air does not harm the skin or lungs; in fact, some patients with psoriasis report relief from itching, and asthmatics may experience less wheezing.